People often collaborate in creating and reviewing documents through annotations, which are overlaid information comments anchored in place over underlying snippets of text or images in office productivity applications, such as word processor programs. Traditionally, two collaboration models have been used: a single-file model and a file-broadcast model. In the single-file model, all collaborators are assumed to work on the same underlying file. Collaborators may relay control of the underlying file via e-mail or a check-in/check-out document management system to add annotations in an orderly manner until the control of the document cycles back to the originator. However, the single-file model presents time and zonal conflicts. Because annotations are anchored in the document to underlying text, simultaneous editing of text by multiple collaborators may lead to annotation conflicts. To preserve comments from one collaborator to another, comments must be changed sequentially such as to not lose changes made by one collaborator over the other.
In the file-broadcast model, the originator of the document is presumed to have distributed the original file either by broadcasting the file to all collaborators through e-mail or via a public forum, such as a Wiki or a message board. Collaborators work on their own copy of the file and propagate annotations back to the originator and the originator then consolidates the feedback. However, the file broadcast model may present annotation-file binding implications. Annotations from two versions of a document with two different owners, separated in space and time, cannot be consolidated until the end of the collaboration life-cycle because annotations are anchored physically in the file. Such physical binding may require either a manual or automated consolidation operation at the end of the collaborative life-cycle by the originator of the document. The file-broadcast model may also present in-progress access control and anchorability implications. If annotation consolidation is desired by anyone other than the originator of the document, post peer-to-peer relationships must be established which can become complex.
Accordingly, a need exists for alternative methods for annotating electronic documents.